little shock means usually dozens volts, for correct grounding it's too much, doesn't matter if it's coming from static or functional leakage current.
there are people feeling 12Vdc/Ac, but normally you should feel discharge of a lot more voltage potential in respect to earth.
what i'm saying, your earth circuit doesn't respect the ohmic maximal value in your country (ie, you felt 50volts, earth must be below 4ogms for example, added with your earth connection to earth central connection, divide those 50V by resistance you should have between your AC earth terminal upto earth of power distribution box, the value is not ok for sure).
lot of theory, bad earth connection for sure. with correct earth equivalent resistance (ohms, no more), you shouldn't feel a thing